1. Field of the Invention
This invention relates to a reliability analyzing system for manufacturing processes, in particular to a reliability analyzing system for manufacturing processes permitting to analyze the reliability of manufacturing and controlling processes and to effect the quality control of manufacturing and controlling processes in view of securing specifications i.e. quality required to products with respect to manufacturing and controlling processes therefor.
2. Description of the Prior Art
Hitherto, as reliability analyzing methods for manufacturing processes, are known "Process FMEA" (cf. e.g. Ford: RELIABILITY METHODS, Failure Mode and Effects Analysis for Processes-Module XIV-A, RELIABILITY OFFICE, NORTH AMERICAN AUTOMOTIVE OPERATIONS, January (1972), which is a method developed for reliability analysis of manufacturing processes on the basis of the FMEA (Failure Mode and Effects Analysis) method utilized for reliability analysis for machinery and tools or systems, and Shimakura and Haneda: QEC activities for IC production, "Hinshitsu" (Quality), Vol. 10, No. 3, pp. 135-203 (1980)).
"Process FMEA" is a method by which defective modes (failure modes) expected to appear during each process are enumerated; the causes giving rise to the defective modes and their influences on products are extracted; and the contents are described in the form of a list for every defective mode of a process. However, since the method is based on descriptions in the form of a list, its descriptive capacity is low and its utilization is limited to analysis of separate defective modes. Consequently, it is not suitable to analyze the reliability of manufacturing and controlling processes as a whole. That is, by "Process FMEA", influences of the defective modes and the causes of their occurrence are described separately for each of the defective modes, and the relation between each of the defective modes and the quality required to the product are not treated in a clear manner. As a result, it has drawbacks that influences on the products provoked by a plurality of defective modes are not clear and further latent defective phenomena are overlooked, etc. Moreover "Process FMEA" is unsuitable for the reliability analysis concerning the positive aspects of the quality, such as increase of the process capacity, shortening of the process, quality guarantee by process changes, etc., because inter-relationships between different processes are not clear.